The present invention relates to a tool for rotary cutting machining with a tool body and a replaceable cutting head detachably attachable to the tool body. The invention also relates to a tool body and a cutting head included in such a tool.
U.S. Pat. No. 5,988,953 A and U.S. Pat. No. 5,971,673 A disclose a known tool, wherein the mutual gripping surfaces of the tool body and the cutting head are conical and widen in the direction towards the rear end of the tool body and the cutting head, respectively, so as to thereby achieve a positive locking in axial direction between the tool body and the cutting head. This positive locking prevents the cutting head from being displaced in axial direction away from the tool body, for instance when the tool is pulled out of a bore drilled by means of the tool. A disadvantage with these conical gripping surfaces is that the tolerance requirements are high for these surfaces and that they are relatively complicated to achieve by means of mechanical machining.
It is desirable to achieve a tool of the type mentioned by way of introduction with a new and favourable design.
In a tool according to an aspect of the invention, the cutting head is prevented from being displaced in axial direction away from the tool body by means of the mutual engagement between the internal gripping surfaces of the tool body and the corresponding external gripping surfaces of the cutting head, the gripping surfaces of the tool body being cylindrical and extending in parallel with the centre axis of the tool body and the gripping surfaces of the cutting head being cylindrical, extending in parallel with the centre axis of the cutting head and having a radius which is larger than the radius of said internal gripping surfaces. The cylindrical external gripping surfaces of the cutting head and the cylindrical internal gripping surfaces of the tool body are dimensioned so as to, by engagement with each other, prevent the cutting head from being displaced in axial direction away from the tool body when the cutting head is attached to the tool body. Consequently, the cutting head is prevented by these cylindrical gripping surfaces from sliding in axial direction away from the tool body, and the cutting head is forced by these cylindrical gripping surfaces to accompany the tool body when the tool body is pulled in axial direction out of a bore drilled by means of the tool. With the solution according to the invention, this axial locking of the cutting head to the tool body is achieved without requiring any conical sections in the mutual gripping surfaces of the tool body and the cutting head or any positive locking in axial direction achieved in any other manner. The coupling portion of the tool body and the coupling portion of the cutting head can thereby be given a shape that is simplified and favourable with respect to the manufacturing of the tool body and the cutting head. Owing to the fact that the gripping surfaces of the tool body are cylindrical and parallel with the centre axis of the tool body, an achievement of these gripping surfaces by mechanical machining of a blank prepared for the formation of a tool body is facilitated, and owing to the fact that the gripping surfaces of the cutting head are cylindrical and parallel with the centre axis of the cutting head, and achievement of these gripping surfaces by mechanical machining of a blank prepared for the formation of a cutting head is facilitated.
According to a favourable embodiment of the invention, a stop surface of a respective coupling leg extends in parallel with the centre axis of the tool body and the corresponding stop surface of the cutting head extends in parallel with the centre axis of the cutting head. By letting the stop surfaces of the tool body be parallel with the centre axis of the tool body, an achievement of these stop surfaces by mechanical machining of a blank prepared for the formation of a tool body is facilitated, and by letting the stop surfaces of the cutting head be parallel with the centre axis of the cutting head, an achievement of these stop surfaces by mechanical machining of a blank prepared for the formation of a cutting head is facilitated.
According to another favourable embodiment of the invention, the internal gripping surfaces of the coupling portion of the tool body are arranged on the inside of a respective one of said coupling legs at the level of the stop surface of the coupling leg, and the external gripping surfaces of the coupling portion of the cutting head are arranged at the level of the stop surfaces of the cutting head. Hereby, the coupling portion of the tool body and the coupling portion of the cutting head can be given a relatively compact design with a comparatively short extension in axial direction.
Other favourable features of the tool according to the invention will appear from the following description.
The invention also relates, according to further aspects thereof, to a tool body and to a cutting head.
Other favourable features of the tool body according to aspects of the invention and the cutting head according to aspects of the invention will appear from the dependent claims and the following description.